Method of manufacturing a burner and a burner thus manufactured

ABSTRACT

A gas burner comprising a tube having a gas supply connection, there being a sleeve partly engaging the outside of the tube and partly spaced therefrom whereby to define a space between the sleeve and the tube presenting a gas expansion chamber, outlet ports in the tube and means placing the chamber in communication with the ports. The burner is manufactured by forming an outlet port in a tube, forming a longitudinal groove in the tube and placing a sleeve having grooves therein over the tube whereby to create the gas expansion chamber and placing the same in communication with the outlets.

United States Patent 151 msoew De Vries, J [451 Apr. 18, W72

[ METHOD OF MANUFACTURING A [56] References Cited BURNER AND A BURNERTHUS Y MANUFACTURED v I FOREIGN PATENTS OR APPLICATIONS [72] Inventor:Hendrik De Vries, Jr., Nijmegen, N etherg ss lands [73] Assignee: N. L.Application S.A., Fribourg, Switzer- Primary yJ land Attorney-Schmidt,Johnson, Hovey & Williams [22] Filed: Apr. 29, 1970 57 ABSTRACT PP N042,703 A gas burner comprising a tube having a gas supply connection,there being a sleeve partly engaging the outside of the [30] ForeignApplication i i Data tube and partly spaced therefrom whereby to definea space between the sleeve and the tube presenting a gas expansion July14, 1969 Netherlands ..6,9l0,775 h b outlet ts i the tube and meansplacing the Jan. 14, 1969 Netherlands ..6,900,55 5 hamber icommunication with the parts, The burner is manufactured by forming anoutlet port in a tube, forming a US. Cl. R, R, longitudinal groove inthe tube and placing a leeve having 7 239/554 grooves therein over thetube whereby to create the gas ex- [5 1] int. ansion chamber and placingthe same in communication with [58] Field of Search 1/349; 239/554, 567;h l

26 Claims, 15 Drawing Figures PATENTEDAPR 18 I972 SHEET 2 0F 6 IIIII FIG7 PATENTEBAPR 18 are SHEET 3 0F 6 METHOD MANUFACTURING A BURNER AND ABURNER THUS MANUFACTURED According to this invention a burner comprisesa tube having a gas supply connection and a sleeve partly engaging theoutside of the tube and being partly located at a distance from thetube, the arrangement being such that gas can flow from the connectioninto the tube and into the space between the sleeve and the tube,outlets being provided in the tube portion not engaged by the sleeve,the sleeve and the tube being so formed that the said space constitutesa gas expansion chamber, and grooves being provided through which gascan pass from the expansion chamber, thence between'the tube and sleeve,to atmosphere in the region of the outlet ports.

In this manner a burner can be obtained which is particularly suitablefor slowly burning types of gas, for example, natural gas, while inaddition the burner operates noiselessly, because pre-mixing ofcombustion air, which produces comparatively high noise, is notemployed. Moreover, the gas can flow at full pressure to the outletports so that the burner has the advantage of an optimum flame pulse, itbeing thus possible to design compact gas-consuming apparatus. Theburner also pennits ready cleaning of the grooves forming auxiliary gasdosing ports, these grooves being readily accessible.

A further advantage of the burner of the invention over burners withpre-mixing of primary combustion air is that the risk of dust beingsucked in by the combustion air is avoided. I

A burner in accordance with the invention can be manufactured in asimple manner by slipping onto a tube having at least one outlet port asleeve having a longitudinal slot and formed so that the parts boundingthe longitudinal slot intimately engage the tube, an intermediate pieceinterconnecting the parts bounding the longitudinal slot being locatedat a distance from the tube wall opposite that part of the tube wallwhere the outlet ports are provided, and grooves being provided betweenthe parts bounding the longitudinal slot and the opposite parts of thetube, which grooves form connections between the expansion chamber andthe edges of the longitudinal slot.

The invention will now be described by way of example with reference tothe accompanying drawings, in which:

FIG. 1 is a perspective view of part of a burner;

FIG. 2 is a perspective view showing the formation of circular groovesin the tube;

FIG. 3 is a perspective view showing a different method of fonning thecircular grooves;

FIG. 4 is a bottom plan of a burner, the sleeve being omitted and theburner being provided on one side with a connecting piece for a supplypipe;

FIG. 5 is a side elevation of the burner shown in FIG. 4, with thesleeve in position;

FIG. 6 is a top plan of the burner of FIG. 4, with the sleeve inposition;

FIG. 7 is a top plan of several burners;

FIG. 8 is a side elevation of the burner of FIG. 7;

FIG. 9 is a side elevation of a second embodiment of a burner;

FIG. 10 is a section through a third embodiment of a burner;

FIG. 11 is a perspective view of part of a fourth'embodiment of aburner;

FIG. 12 is a side elevation of the burner of FIG. 11, part of the sleevebeing broken away;

FIG. 13 is a bottom plan of the part of the burner shown in FIG. 12; l

FIG. 14 is a perspective view ofpartof a fifth embodiment of a burner;and

FIG. 15 is partly a sectional and partly a side elevation of the burnerof FIG. 14.

As shown in FIG. 1, the burner comprises a tube 1 having a plurality ofcircular indents or grooves 2. The bottom side of the tube has alongitudinal groove or depression 3, in which a few openings 4 areprovided. The top side of the tube has a thinner portion 5 obtained byremoving material to form a face 6 on the tube. This thinner portion 5has a plurality of gas outlet ports 7 of very small diameter. Fornatural gas this diameter will be of the order of 0.2 mm. The ports 7are located in the same planes as the grooves 2. The openings 4 are oflarger diameter than the ports 7, but the openings 4 are provided in asmaller number, for example, only one.

The tube 1 is partly surrounded as shown by a sleeve 8 having alongitudinal slot, the sleeve 8 being arranged so that the outlet ports7 open to atmosphere between the sleeve parts engaging the tube so as toengage it intimately and bounding the longitudinal slot, while anintermediate or central piece of the sleeve forms, together with thedepression 3, a chamber 9 which communicates with the outlet opening(s)4 and the flow channels formed by the indents 2. The space serves as anexpansion space for the gas supplied.

The burner operates as follows: The gas to be burnt is supplied at areduced pressure to the interior of the tube I and can flow out from theports 7. The rate of flow of gas from the ports 7 exceeds, however, therate of combustion of the gas, so

that a flame emanating from an outlet port 7 would extinguish itself,except that some of the gas also flows through the opening(s) 4 to theexpansion space 9 from where the gas can escape along the indents 2 and,owing to the matching proportioning of the opening(s) 4 and the grooves2, at a considerably lower pressure, and can be ignited as auxiliaryflames 10, which can ignite the gas emanating from the ports 7continuously to form main flames 11. Since the gas is conducted withoutreduction of pressure to the ports 7, main flames 11 of a high flamepulse are produced, so that a very compact apparatus can be designed.The gas does not contain premixed combustion air, so that the flamesburn substantially silently. With this arrangement is is possible toclean the depressions or indents, because they are readily accessible.

FIGS. 2 and 3 illustrate two possibilities for forming the circularindents 2. As shown in FIG. 2, a commercially available tube 1 ispressed against an auxiliary roller 12, which is provided with circularridges l3 equally spaced apart. The tube 1 and roller 12 are rolled onealong the other under pressure so that the ridges l3 produce the indents2.

FIG. 3 shows a further possibility of forming the indents 2. The tube 1is rolled over a plate 14 provided at regular intervals with parallelridges 15. The tube is rolled in the direction of the ridges 15, whichthus produce the circular indents 2. The grooves may alternatively beprovided by a chipping operation on a kind of lathe. The longitudinalgroove 3 may be rolled in the tube. The face 6 may be provided bymilling or .abrading a local part of the tube, but in a variant a hollowgroove may be milled out so that the thickness of the material isreduced. This has the advantage that the small outlet ports need bepierced only through a thin layer of metal and rupture or wear of thedrills used is reduced, the diameter of the drills being about 0.2 mm.After this pre-treatment of the tube, the sleeve can be slipped onto it.

FIGS. 4, 5 and 6 show a burner manufactured as described above andprovided at one end with a connecting piece I6 for a gas supply pipe,the other end of the tube being closed by pinching in the manner usuallyapplied to a tube of toothpaste. This closure is designated 17. FIG. 4does not show the sleeve 8 in order to show the position of thelongitudinal groove 3 and an opening 4. The burner shown in FIGS. 4, 5and 6 is preferably connected with a horizontal gas supply tube, withwhich a plurality of the burners may be connected, so that a burnerassembly is obtained suitable for use, for example, in a gas geyser or acentral-heating boiler. As compared with the power involved thestructure can be very compact so that the Construction of the wholeheating apparatus is compact.

FIGS. 7 and 8 show a further embodiment of the invention. A number oftubes 1, provided on two sides with indents 2, longitudinal grooves 3(now shown), faces 6 and outlet ports 4 and 7 in the manner describedabove, are connected with a main supply pipe 18, which communicates withthe interiors of the tubes 1. The tubes 1 are arranged so that theyproject on either side equal distances beyond the pipe 18. The two endsof each tube 1 are pinched to form closures 17. On either side of thepipe 18, a sleeve 8 is slipped on to each tube 1. In this way a batteryor multiple burner is formed which may be employed also in a gas geyseror a heating boiler, and whose structure is also very compact.

FIG. 9 shows a further embodiment of the invention, particularlysuitable for converting town-gas burners into naturalgas burners. A tube1, formed in the manner described above, is provided at the centre witha connecting piece 19 which may be screwed onto existing gas pipes afteran existing burner has been unscrewed. This connecting piece 19communicates with the interior of the tube 1. In this case the expansionchambers 9 are provided with an inlet port 21, which is provided at oneend of the longitudinal groove. The ends of the tube 1 are closed bycaps 20.

The upper side of the tube 1 has two faces 22 and 23 milled at a givenangle to each other, so that a double row of V- shaped flames isobtained. It is possible to retain a horizontal face 24 on the upperside, so that W-shaped flames can be produced, as shown.

An important advantage of the burners described above resides in thefacts that the basic material is cheap and commercially available andthat machining can be carried out by simple means. Other advantages arethat the burners can be compact, and gas can burn noiselessly, becauseit is not previously mixed with combustion air. A further advantage isthat the burner may be manufactured in a great length and be cut todesired lengths. The range of uses is therefore wide.

The burner shown in FIGS. 11 to 13 comprises a tube 25, which is milledor smoothed on the upper side for obtaining a comparatively thin upperportion 26. The upper portion 26 is provided with bores 27, whichtogether form a row of outlet ports extending in the longitudinaldirection of the tube. The diameter of these ports may be small and inthe case of natural gas will be of the order of 0.2 mm. Approximatelydiametrically opposite the outlet ports 27 one or more flow ports 28 areprovided in the wall of the tube. The diameter of a port 28 exceeds thatof a port 27, but, in general, the number of ports 28 will beconsiderably less than the number of ports 27. In many cases a singleport 28 will be sufficient, if the length of the tube is not too great.

The tube 25 is slipped into a sleeve 29, which then partly surrounds thetube 25 and is provided with a longitudinal slot extending in thedirection of the length of the tube. The elongated slot is bounded bytwo parts 30 and 31 of the sleeve, which parts intimately fit around thetube 25. The parts 30 and 31 are interconnected by an intermediate piece32, which is located at a distance from the tube 1 so that between theintermediate piece 22 and the opposed tube portion a chamber 33 isformed. The parts 30 and 31 are also provided with depressions orindents 34, which form channels or grooves extending between the chamber33 and the edges of the parts 30 and 31 bounding the elongated slot ofthe sleeve 29. The depressions 34 are preferably located so that theirlongitudinal axes are located in planes at right angles to the axis ofthe tube 25. When the tube is slipped into the sleeve 29 it can bearranged that the prolongations of the longitudinal axes of twodepressions 34 in the parts 30 and 31 intersect at least approximatelythe center line of an outlet port 27. Each flow port 28 is arranged sothat it opens out into the chamber 33.

A gas supply connection may be provided at one end of the tube 1. Afurther possibility for connection of a gas supply pipe is illustratedin FIGS. 12 and 13, from which it will be apparent that prior to theapplication of the sleeve a plate 35 is secured to the tube 1, whichplate is located in the chamber 33 when the sleeve 29 is arranged inplace. The dimensions of the plate are such that the portions of thechamber 33 located on either side of the plate 35 are in opencommunication with each other. The wall of the sleeve 29, the plate 35and the tube 25 may be provided with registering holes 36 for connectinga gas supply duct.

The burner shown in FIGS. 11 to 13 can be manufactured in a simplemanner, since the tube 25 may be a commercially available tube and thesleeve 29 can be shaped readily in the desired form by means'of rollersand can be provided with the depressions or indents 34. Piercing of theoutlet ports 27 and of the flow port(s) 28 in the tube 25 can be readilycarried out by drilling. An advantage is that the upper side of the tube25 is flattened so that the wall thickness of the tube 25 at the area ofthe outlet ports 27 is comparatively small which reduces drill wear.Flattening of the upper side is not absolutely necessary. After the tube25 and the sleeve 29 have been machined in the manner described above,the tube 25 need only be slipped into the sleeve 29 in the correctposition so that the depressions 34 are opposite the outlet ports 27.The outlet ports 27 may be made in the tube 25 both before or afterapplication of the sleeve. Then a gas supply connection can beestablished with the tube 25, or a number of these burners may beassembled to form a grating or the like, which is connected with acommon supply pipe, after which the burner is ready for use. The ends ofthe tube and the ends of the chamber 33 must be closed effectively andthis may be achieved by pinching one end of the tube 25 as in thepreceding embodiments.

The burner operates as follows:

The gas to be burnt is supplied without reduction of pressure to theinterior of the tube 25 and can escape to the outside via the outletports 27. The rate of flow of the gas from the ports is, however, higherthan the rate of combustion of the gas, so that without furtherprecautions the gas escaping from the outlet ports 27 would not burn.However, a portion of the gas supplied to the tube also passes throughthe port(s) 28 into the chamber 33, which fonns an expansion space, fromwhere the gas can escape at considerably reduced pressure through thedepressions or grooves 34, the port(s) 28 and the grooves 34 beingsuitably proportioned. The gas slowing from the grooves or auxiliary gaspassages 34 can be ignited so that auxiliary flames 37 are formed. Bymeans of these auxiliary flames 37 the gas flowing from the outlet ports27 is ignited and kept burning, so that main flames 38 are formed. Sincethe gas is fed without reduction of pressure to the outlet ports 27,main flames 38 having a high flame pulse are produced.

The burner shown in FIGS. 14 and 15 comprise a tube 40, which is milledor flattened on the upper side to obtain a comparatively thin upperportion 41. The upper portion 41 is provided with bores 42 which form arow of outlet ports extending in the longitudinal direction of the tube.The diameter of these ports may be small and, for example, with naturalgas, will be of the order of 0.2 mm. The wall portion 43 of the tubelocated approximately diametrically opposite the outlet ports 42 isflattened so that this portion is parallel to a plane at right angles tothe center lines of the row of outlet ports 42.

The tube 40 is slipped into a sleeve 44, which partly surrounds the tubeand which is provided with an elongated slot extending in the directionof length of the tube and bounded by the edges of two parts 45 and 46 ofthe sleeve 44. The parts 45 and 46, fitting intimately around the tube40, are interconnected by a U-shaped intermediate piece fonned by twolimbs 47 and 48 lying on the edges of the parts 45 and 46 and a web 49interconnecting the lower edges of the limbs and extending at rightangles to them and parallel to the portion 43 of the tube 40.

The intermediate piece 47, 48, 49 encloses an insert of generallyV-shaped section and formed by two plates 50 and 51 lying abutting thelimbs 47 and 48 as shown, the plates terminating at a given distanceabove the web 49 in upwardly inclined, converging plates 52 and 53,integral with the plates 50 and 51. The upper ends of the plates 52 and53, which ends are near the portion 43 of the tube 40, areinterconnected by a plate 54 engaging the portion 43 and integral withthe plates 52 and 53. The plates 52 and 53 are provided with ports 55 sothat the plates 52 and 53 form a kind of perforated grating.

In the parts 45 and 46 of the sleeve 44 engaging the tube 40 depressionsor indents 56 are provided, which form flow channels via which thechamber formed by the intermediate piece 44 and the wall portion 43 ofthe tube communicates with atmosphere.

The burner also has a supply pipe 57 which extends across the chamberbounded by the intermediate piece 44 and into the interior of the tube40. The portion of the supply pipe 57 in the tube 40 has a bore 58 ofcomparatively large diameter forming an outlet port. The portion of thesupply pipe 57 in the chamber bounded by the intermediate'piece 44 isprovided with two smaller outlet ports 59.

This burner can be manufactured in a simple manner because the variousparts can be readily shaped by rolling, while the various bores andconnections can be provided in a comparatively simple manner.

ln operation the gas to be burnt is supplied at non reduced pressure viathe supply pipe 57, the gas flowing at this pressure into the tube 40and from there through the ports 42 to atmosphere. The rate of escape ofthe gas from the ports 42 exceeds, however, the rate of combustion ofthe gas so that without further steps the gas flowing from the outletports 42 would not burn. A portion of the gas supplied by the pipe 57also flows through the ports 59 to the space formed by the expansionchamber, bounded by the intermediate piece 44. From this chamber the gascan flow through the flow channels 56, while a uniform distributionamong the channels 56 is obtained by the perforated partitions orgratings 52 and 53. The gas flows from the channels 56 at acomparatively low rate owing to the reduction of pressure in theexpansion chamber, and can be ignited, so that auxiliary flames areobtained which ignite the gas flowing from the outlet ports 42, whichgas is then kept burning. Since the gas is supplied without pressurereduction to the outlet ports 42 main flames having a high flame pulseare obtained.

Since the gas is not previously mixed with combustion air, the burnerwill operate quietly. Since the gas can flow at full pressure to theoutlet ports and since a high flame pulse is obtained, a comparativelycompact structure of the combustion chamber, and hence a compactconstruction of the gas consuming apparatus, may be obtained. Theauxiliary gas passages obtained by the indents 56 are readily accessibleand can be cleaned readily. Since no combustion air is previously mixedwith the gas, there is no risk that dust carried along by the combustionair will block the outlet ports. Owing to the ample size of theexpansion chamber, bounded by the intermediate piece 44 and the wallportion 43 of the tube 40, clogging of this chamber by deposition ofsubstances in the gas is not likely to occur.

The height of the intermediate piece 44 at the wall 43 of the tube 40 ispreferably about 60 percent of the diameter of the tube 40 and the widthof the intermediate piece is preferably about 80 percent of thatdiameter. The height of the tube at right angles to the face 43 ispreferably about 85 percent of the diameter of the tube.

The burners described above can be manufactured in a simple manner fromconventional, commercially available material, such as pipes and/orplates, which need be subjected only to comparatively simple operations,while the various parts can be readily connected to each other.

What we claim is:

1. A burner comprising a tube having a gas supply connection and asleeve partly engaging the outside of the tube and being partly locatedat a distance from the tube, the arrangement being such that gas canflow from the connection into the tube and into the space between thesleeve and the tube, outlet ports being provided in the tube portion notengaged by the sleeve, the sleeve and the tube being so formed that thesaid space constitutes a gas expansion chamber, and grooves beingprovided through which gas can pass from the expansion chamber, thencebetween the tube and sleeve, to atmosphere in the region of the outletports.

2. A burner as claimed in claim 1 wherein the grooves are arranged-sothat the two openings of the grooves located one each side of the tubeand an outlet port are located in a plane at right angles to thelongitudinal axis of the tube.

3. A burner as claimed in claim 1 wherein the grooves are provided inthe wall of the tube.

4. A burner as claimed in claim 1 wherein the grooves are provided inthe parts of the sleeve engaging the tube.

5. A burner as claimed in claim 1 wherein the sleeve has an at leastsubstantially circular section and the tube is provided with alongitudinal groove to form'the expansion chamber.

6. A burner as claimed in claim ll wherein the wall thickness of thetube at the area of the outlet ports is smaller than the wall thicknessof the further part of the tube.

7. A burner as claimed in claim 1 wherein outlet ports are provided atregular intervals in the wall of the tube so that the outlet ports arelocated at least substantially in one row extending substantially in thedirection of length of the tube.

8. A burner as claimed in claim 1 wherein there is an intermediate pieceinterconnecting the two sleeve parts intimately engaging the tube whichis bent over relatively to said parts so that the intermediate piece islocated at a distance from the tube wall so that between the tube walland the intermediate piece an expansion chamber extends in the directionof length of the tube.

9. A burner as claimed in claim 8 wherein the portion of the tube walllocated in the chamber has secured to it a plate to fonn a connection.

10. A burner as claimed in claim 9 wherein the width of the plate issmaller in sectional area than the width of the chamber.

11. A burner as claimed in claim 1 wherein the two sleeve parts engagingthe tube are interconnected by means of an intermediate piece, thesectional area of which has the shape of a substantially rectangular U.

12. A burner as claimed in claim 1 wherein the wall portion of the tubeprovided with outlet ports and located between the sleeve parts engagingthe tube is flattened.

13. A burner as claimed in claim 12 wherein the flattened part of thetube extends parallel to the web between the limbs of the intermediatepiece.

14. A burner as claimed in claim 1 wherein a gas supply pipe isconnected with the tube and the tube wall is provided with at least oneopening through which gas can flow from the tube to the expansionchamber.

15. A burner as claimed in claim 14 wherein both the tube and theexpansion chamber communicate directly with a gas supply pipe.

16. A burner as claimed in claim 11 wherein a supply pipe is providedwhich extends transversely of the direction of length of the tube andwhich extends through the U-shaped intermediate piece as far as into theinterior of the tube, whilst the end of the supply pipe located insidethe tube and the portion of the supply pipe located in the expansionchamber are provided with an opening.

17. A burner as claimed in claim 16 wherein a perforated partition isprovided between the grooves forming flow channels and the opening ofthe supply pipe located in the expansion chamber bounded by the tube.

18. A burner as claimed in claim 17 wherein the U-shaped intermediatepiece comprises two apertured plates forming partitions, which extendfrom the limbs of the intermediate piece obliquely upwards up to theflattened tube portion, whilst the ends of the plates located near theflattened tube portion are interconnected by a plate engaging theflattened portion, whereas the ends remote from the flattened portionare integral with plates extending along the limbs of the intermediatepiece up to the web between the two limbs.

19. A method of manufacturing a burner wherein a tube having at leastone outlet port is engaged by a sleeve having an elongated slot, thesleeve and the tube being formed, and the sleeve being slipped onto thetube, so that the parts bounding the elongated slot intimately engagethe tube and an intermediate piece interconnecting the said two parts islocated at a distance from the tube and opposite that part of the tubein which the outlet port is provided, whilst between the said two partsand the opposite parts of the tube grooves are provided forming acommunication between the space between the intermediate piece of thesleeve and the tube and the edges of the elongated slot.

20. A method as claimed in claim 19 wherein, before insertion of thetube into the sleeve, partly circular indents are made at regularintervals in the tube, and a longitudinal groove is also made therein.

21. A method as claimed in claim 20 wherein in the longitudinal grooveone or more openings are made in the tube wall.

22. A method as claimed in claim 19 wherein, at the area of the smalleroutlet ports the wall thickness of the tube is reduced for providingsaid ports.

23. A method as claimed in any of claims 18 to 22 wherein at least oneend of the tube is closed by pinching it.

24. A method as claimed in claim 19 wherein, before the insertion of thetube into the sleeve, the sleeve parts engaging the tube are providedwith grooves or depressions.

25. A method as claimed in claim 19 wherein, before the insertion of thetube, the intermediate piece inter-connecting the two sleeve partsengaging the tube is bent over relatively to the sleeve parts.

26. A method as claimed in claim 19 wherein, before application of thesleeve, the part of the tube located opposite the intermediate piece ofthe sleeve has secured to it a plate to establish a gas supplyconnection.

1. A burner comprising a tube having a gas supply connection and asleeve partly engaging the outside of the tube and being partly locatedat a distance from the tube, the arrangement being such that gas canflow from the connection into the tube and into the space between thesleeve and the tube, outlet ports being provided in the tube portion notengaged by the sleeve, the sleeve and the tube being so formed that thesaid space constitutes a gas expansion chamber, and grooves beingprovided through which gas can pass from the expansion chamber, thencebetween the tube and sleeve, to atmosphere in the region of the outletports.
 2. A burner as claimed in claim 1 wherein the grooves arearranged so that the two openings of the grooves located one each sideof the tube and an outlet port are located in a plane at right angles tothe longitudinal axis of the tube.
 3. A burner as claimed in claim 1wherein the grooves are provided in the wall of the tube.
 4. A burner asclaimed in claim 1 wherein the grooves are provided in the parts of thesleeve engaging the tube.
 5. A burner as claimed in claim 1 wherein thesleeve has an at least substantially circular section and the tube isprovided with a longitudinal groove to form the expansion chamber.
 6. Aburner as claimed in claim 1 wherein the wall thickness of the tube atthe area of the outlet ports is smaller than the wall thickness of thefurther part of the tube.
 7. A burner as claimed in claim 1 whereinoutlet ports are provided at regular intervals in the wall of the tubeso that the outlet ports are located at least substantially in one rowextending substantially in the direction of length of the tube.
 8. Aburner as claimed in claim 1 wherein there is an intermediate pieceinterconnecting the two sleeve parts intimately engaging the tube whichis bent over relatively to said parts so that the intermediate piece islocated at a distance from the tube wall so that between the tube walland the intermediate piece an expansion chamber extends in the directionof length of the tube.
 9. A burner as claimed in claim 8 wherein theportion of the tube wall located in the chamber has secured to it aplate to form a connection.
 10. A burner as claimed in clAim 9 whereinthe width of the plate is smaller in sectional area than the width ofthe chamber.
 11. A burner as claimed in claim 1 wherein the two sleeveparts engaging the tube are interconnected by means of an intermediatepiece, the sectional area of which has the shape of a substantiallyrectangular U.
 12. A burner as claimed in claim 1 wherein the wallportion of the tube provided with outlet ports and located between thesleeve parts engaging the tube is flattened.
 13. A burner as claimed inclaim 12 wherein the flattened part of the tube extends parallel to theweb between the limbs of the intermediate piece.
 14. A burner as claimedin claim 1 wherein a gas supply pipe is connected with the tube and thetube wall is provided with at least one opening through which gas canflow from the tube to the expansion chamber.
 15. A burner as claimed inclaim 14 wherein both the tube and the expansion chamber communicatedirectly with a gas supply pipe.
 16. A burner as claimed in claim 11wherein a supply pipe is provided which extends transversely of thedirection of length of the tube and which extends through the U-shapedintermediate piece as far as into the interior of the tube, whilst theend of the supply pipe located inside the tube and the portion of thesupply pipe located in the expansion chamber are provided with anopening.
 17. A burner as claimed in claim 16 wherein a perforatedpartition is provided between the grooves forming flow channels and theopening of the supply pipe located in the expansion chamber bounded bythe tube.
 18. A burner as claimed in claim 17 wherein the U-shapedintermediate piece comprises two apertured plates forming partitions,which extend from the limbs of the intermediate piece obliquely upwardsup to the flattened tube portion, whilst the ends of the plates locatednear the flattened tube portion are interconnected by a plate engagingthe flattened portion, whereas the ends remote from the flattenedportion are integral with plates extending along the limbs of theintermediate piece up to the web between the two limbs.
 19. A method ofmanufacturing a burner wherein a tube having at least one outlet port isengaged by a sleeve having an elongated slot, the sleeve and the tubebeing formed, and the sleeve being slipped onto the tube, so that theparts bounding the elongated slot intimately engage the tube and anintermediate piece interconnecting the said two parts is located at adistance from the tube and opposite that part of the tube in which theoutlet port is provided, whilst between the said two parts and theopposite parts of the tube grooves are provided forming a communicationbetween the space between the intermediate piece of the sleeve and thetube and the edges of the elongated slot.
 20. A method as claimed inclaim 19 wherein, before insertion of the tube into the sleeve, partlycircular indents are made at regular intervals in the tube, and alongitudinal groove is also made therein.
 21. A method as claimed inclaim 20 wherein in the longitudinal groove one or more openings aremade in the tube wall.
 22. A method as claimed in claim 19 wherein, atthe area of the smaller outlet ports the wall thickness of the tube isreduced for providing said ports.
 23. A method as claimed in any ofclaims 18 to 22 wherein at least one end of the tube is closed bypinching it.
 24. A method as claimed in claim 19 wherein, before theinsertion of the tube into the sleeve, the sleeve parts engaging thetube are provided with grooves or depressions.
 25. A method as claimedin claim 19 wherein, before the insertion of the tube, the intermediatepiece inter-connecting the two sleeve parts engaging the tube is bentover relatively to the sleeve parts.
 26. A method as claimed in claim 19wherein, before application of the sleeve, the part of the tube locatedopposite the intermediate piece of the sleeve has secured to it a plateto establish a gas supply connection.